Bearing sealing device and bearing sealing mechanism capable of preventing the leakage of grease

ABSTRACT

There is provided a bearing sealing device capable of substantially completely preventing a leak of grease. A taper end portion of an axial extension of the bearing sealing device has an opposite surface and a rake face that forms a specified rake angle with the opposite surface. The opposite surface forms a narrow passage between the opposite surface and an outer peripheral surface of an inner ring. The narrow passage allows air to pass easily, but it allows grease to hardly pass therethrough. Further, the axial extension includes part of a core metal that extends axially and has its foremost end located axially inside an axial outermost end of the outer peripheral surface of the inner ring. Grease moving axially outwardly on the outer peripheral surface is moved along the rake face of the taper end portion and then guided along a cover portion of the bearing sealing device to an outer ring. The part of the core metal prevents the axial extension from being bent radially outwardly by a centrifugal force.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a bearing sealing device and a bearingsealing mechanism for outer ring rotating type bearings such as bearingsfor axles, and bearings for engine accessories like outer ring rotatingtype water pumps, idlers and tensioners.

2. Description of the Prior Art

Conventionally, as a bearing sealing device of this type, there is oneas shown in FIG. 9. The sealing device includes a main lip 73 that isput in slidable contact with a side surface 72A located axiallyoutwardly of an annular groove 72 formed on an outer peripheral surface71A of an inner ring 71, and an auxiliary lip 75 provided withinterposition of a specified clearance to a slant side surface 72Barranged opposite to the side surface 72A. The main lip 73 and theauxiliary lip 75 are converged at their roots to be integrated into onebody, and a radially outward end portion (not shown) thereof is fixed toan outer ring (not shown).

In the sealing device, the auxiliary lip 75 intercepts grease frominside the bearing. Further, the grease that has passed around theauxiliary lip 75 is intercepted by the main lip 73.

However, in the above prior art bearing sealing device, a pressure forceexerted from the main lip 73 on the side surface 72A is sometimesweakened by a centrifugal force depending on use conditions, andtherefore the grease that has passed around the auxiliary lip 75possibly passes around the main lip 73. The above also results in theproblem that the leak of the grease is incompletely prevented.

SUMMARY OF THE INVENTION

The object of the present invention is therefore to provide a bearingsealing device and a bearing sealing mechanism capable of substantiallycompletely preventing the leak of grease.

In order to achieve the above object, the present invention provides abearing sealing device which is provided between an outer ring and aninner ring of a bearing in which the outer ring rotates, seals a spacebetween the outer ring and the inner ring, and is securely fixed to theouter ring so as to rotate together with the outer ring, comprising:

a fixed portion fixed to the outer ring;

a cover portion which extends in a radially inward direction of theouter ring from the fixed portion and covers the space between the outerring and the inner ring; and

an axial extension which is made of an elastic material and extends inan axially inward direction of the outer ring from the cover portion,wherein

the axial extension includes a taper end portion having an oppositesurface which is opposed to an outer peripheral surface of the innerring and forms between the opposite surface and the outer peripheralsurface of the inner ring a narrow passage having a specified narrownesssuch that air is allowed to pass comparatively easily and oil is allowedto pass comparatively hardly, and a rake face forming a specified rakeangle with the opposite surface; and the fixed portion, the coverportion and the axial extension respectively include part of a coremetal, said core metal extending axially inwardly from the cover portionup to a position on a radially outer side of the outer peripheralsurface of the inner ring, where a foremost end of the core metal ispositioned in the vicinity of the taper end portion.

According to the bearing sealing device of the present invention, theopposite surface of the taper end portion forms the narrow passagebetween the opposite surface and the outer peripheral surface of theinner ring. The narrow passage allows air to pass comparatively easily,but it allows oil such as grease to pass comparatively hardlytherethrough. Therefore, the grease moving axially outwardly on theouter peripheral surface of the inner ring is moved along the rake facehaving the specified rake angle upon reaching the taper end portion.Then, the grease moved along the rake face is guided to the outer ringalong the cover portion.

Therefore, according to the present invention, the possible leak of thegrease is prevented substantially completely.

Furthermore, according to the present invention, the axial extensionincludes the part of the core metal, and the foremost end of the coremetal axially extends in the vicinity of the taper end portion up to aposition on the inner side of the outer peripheral surface of the innerring. Therefore, the axial extension is prevented from being bentradially outwardly by a centrifugal force or another external forcegenerated when the outer ring is rotated. Therefore, even when acentrifugal force is generated due to the rotation of the outer ring,the possible leak of the grease is always prevented substantiallycompletely. Furthermore, by virtue of the existence of the core metal,the clearance between the axial extension and the outer peripheralsurface of the inner ring can be set with high accuracy.

Furthermore, in an embodiment, the taper end portion has at its axiallyinnermost end a recess portion that is recessed radially outwardly fromthe opposite surface that forms the narrow passage and recessed axiallyoutwardly from the foremost end of the rake face.

With the above arrangement, the grease that has axially moved along theouter peripheral surface of the inner ring and reached the taper endportion is firstly caught in the recess portion at the axially innermostend. Then, the mass of the grease is retained in the recess portion.Therefore, an oil component of the grease is intercepted by the mass ofgrease, so that the oil component of the grease is prevented fromentering the narrow passage.

Furthermore, in an embodiment, the axial extension has a recess portionthat is located axially outwardly with respect to the taper end portionand recessed radially outwardly with respect to the opposite surface ofthe taper end portion.

With this arrangement, the grease that has accidentally passed aroundthe taper end portion is caught in the recess portion. Therefore, thepossible leak of the grease is more surely prevented.

Furthermore, in an embodiment, the part of the core metal in the axialextension has an annular configuration and exists continuously around anentire peripheral surface of the inner ring.

Therefore, according to the part of the core metal, the axial extensionis substantially completely prevented from being bent radially outwardlyby the centrifugal force throughout the entire peripheral surface.Therefore, even when a centrifugal force is generated due to therotation of the outer ring, the possible leak of the grease is alwaysprevented substantially completely.

Furthermore, in an embodiment, there is provided a crown-shaped retainerthat is made of resin and holds rolling members arranged between theouter ring and the inner ring. The retainer has a projection includingan opposite surface that is provided oppositely to the outer peripheralsurface of the inner ring axially inwardly with respect to the taper endportion, and forms between the opposite surface and the outer peripheralsurface of the inner ring a narrow passage having such a specifiednarrowness that air is allowed to easily pass and oil is allowed tohardly pass.

According to the above embodiment, the narrow passage formed by theprojection of the retainer intercepts the grease in advance of the taperend portion. Therefore, the possible leak of the grease is more surelyprevented.

Furthermore, in an embodiment, a distance L1 between the retainer thatholds the balls arranged between the outer ring and the inner ringaxially inwardly with respect to the axial extension and the rake faceof the taper end portion of the axial extension is set not smaller thana distance L2 (L1≧L2) between the retainer and the outer peripheralsurface of the inner ring.

The present inventor and others have confirmed through an experimentthat, when the balls are rotating while rolling between the outer ringand the inner ring, a lubricating oil circulates in a route of(balls)→(a space between the outer peripheral surface of the inner ringand the retainer)→(a space between the rake face of the taper endportion of the axial extension and the retainer)→(a space between thecover portion and the retainer)→(a space between the retainer and theouter ring)→(balls).

Then, with the distance L1 between the retainer and the rake face of thetaper end portion set not smaller than a distance L2 (L1≧L2) between theretainer and the outer peripheral surface or the inner ring in a mannerof the present embodiment, the lubricating oil path through the spacebetween the rake face of the taper end portion of the axial extensionand the retainer is made wider than the lubricating oil path through thespace between the outer peripheral surface of the inner ring and theretainer. With this arrangement, the lubricating oil from the spacebetween the outer peripheral surface of the inner ring and the retaineris guided to the space between the rake face of the taper end portion ofthe axial extension and the retainer, and the lubricating oil is made tohardly intrude into the space between the inner ring and the taper endportion. Therefore, the present embodiment has the effect of preventingthe lubricating oil from intruding into the space between the inner ringand the taper end portion. Therefore, in cooperation with the sealingeffect produced by the taper end portion, the possible leak of thelubricating oil is more surely prevented.

Furthermore, there is provided a bearing sealing mechanism comprising:

a bearing sealing device which is provided between an outer ring and aninner ring of a bearing in which the outer ring rotates, seals a spacebetween the outer ring and the inner ring, and is securely fixed to theouter ring so as to rotate together with the outer ring; and

a retainer which holds rolling members arranged between the outer ringand the inner ring axially inwardly with respect to the bearing sealingdevice, wherein

said bearing sealing device has

a fixed portion fixed to the outer ring

a cover portion which extends radially inwardly from the fixed portionand covers a space between the outer ring and the inner ring, and

a seal portion which extends radially inwardly and axially inwardly fromthe cover portion toward an outer peripheral surface of the inner ring,said seal portion having an opposite surface which is opposed to theouter peripheral surface of the inner ring, and forms between theopposite surface and the outer peripheral surface of the inner ring anarrow passage having a specified narrowness such that air is allowed topass comparatively easily and oil is allowed to pass comparativelyhardly, and wherein

said retainer has a configuration such that a distance D1 between theretainer and the seal portion is set not smaller than a distance D2(D1≧D2) between the retainer and the outer peripheral surface of theinner ring.

According to the above embodiment, by virtue of the dimensional settingof D1≧D2, a lubricating oil path through the space between the sealportion and the retainer is made wider than a lubricating oil paththrough the space between the outer peripheral surface of the inner ringand the retainer.

With the above arrangement, the lubricating oil from the space betweenthe outer peripheral surface of the inner ring and the retainer isguided to the space between the seal portion and the retainer, and thelubricating oil is made to hardly intrude into the space between theinner ring and the seal portion. Therefore, the present embodiment hasthe effect of preventing the lubricating oil from intruding into thespace between the inner ring and the seal portion. Therefore, incooperation with the sealing effect produced by the taper end portion,the possible leak of the lubricating oil is more surely prevented.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will become more fully understood from thedetailed description given hereinbelow and the accompanying drawingswhich are given by way of illustration only, and thus are not limitativeof the present invention, and wherein:

FIG. 1A is a sectional view of a bearing sealing device according to afirst embodiment of the present invention;

FIG. 1B is a sectional view of an essential part of a modificationembodiment of the first embodiment;

FIG. 1C is a sectional view of an essential part of another modificationembodiment of the first embodiment;

FIG. 2 is a sectional view of a second embodiment of the presentinvention;

FIG. 3 is a sectional view of a third embodiment of the presentinvention;

FIG. 4 is a sectional view of a fourth embodiment of the presentinvention;

FIG. 5 is a sectional view of a fifth embodiment of the presentinvention;

FIG. 6 is a view showing dimensions of an essential part of a bearingsealing mechanism for explaining an exemplified experiment of leak ofgrease;

FIG. 7 is a graph showing a regression curve of a relation between adimension and the leak of the grease in the above experiment;

FIG. 8 is a graph showing a regression curve of a relation between adimension C and the leak of the grease in the above experiment; and

FIG. 9 is a view showing the structure of a prior art bearing sealingdevice.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention will be described in detail below based onembodiments thereof with reference to the accompanying drawings.

First Embodiment

FIG. 1A shows a bearing sealing device according to a first embodimentof the present invention. This bearing sealing device is arrangedbetween an outer ring 1 and an inner ring 2 of a bearing in which theouter ring 1 rotates, and seals a space between the outer ring 1 and theinner ring 2. The bearing has a plurality of balls 3 arranged in acircular ring form between the outer ring 1 and the inner ring 2. To theplurality of balls 3 is fitted a crown-shaped plastic retainer 5.

The first embodiment has a sectionally bracket-shaped core metal 11 andan elastic portion 12 that is formed of an elastic material and fixedtightly to the core metal 11. The first embodiment includes a fixedportion 13 fit in and secured to a recess 4 at an axial end portionformed on an inner peripheral surface 1A of the outer ring 1, and acover portion 15 that extends radially inwardly from the fixed portion13 and covers a space between the outer ring 1 and the inner ring 2. Thefirst embodiment further includes an axial extension 16 that extendsaxially inwardly from the cover portion 15 and a radial extension 17that extends radially inwardly from the cover portion 15. Each part ofthe core metal 11 is included in the fixed portion .[.12.]..Iadd.13.Iaddend., the cover portion 15 and the axial extension 16.

The axial extension 16 has a taper end portion 18. The taper end portion18 has an opposite surface 20 that is opposite to an outer peripheralsurface 2A of the inner ring 2 and forms a narrow passage 19 between theopposite surface 20 and the outer peripheral surface 2A of the innerring 2, and a rake face 21 which forms a specified rake angle (about45°) with the opposite surface 20.

The core metal 11 has a part 11A that extends axially inwardly from thecover portion 15. In regard to the part 11A, its foremost end 11A-1 ispositioned in the vicinity of the taper end portion 18. Further, theforemost end 11A-1 is placed axially inwardly with respect to an axialoutermost end 2A-1 of the outer peripheral surface 2A of the inner ring2.

The radial extension 17 abuts on a side wall 22A located axiallyoutwardly of a radially recessed annular groove 22 formed at an axialend portion adjacent to the outer peripheral surface 2A of the innerring 2. The radial extension 17 has axially penetrating notches 23. Thenotches 23 are formed in a plurality of portions of the radial extension17 circumferentially at specified intervals.

According to the bearing sealing device having the above construction,the opposite surface 20 of the taper end portion 18 forms a narrowpassage 19 between the opposite surface 20 and the outer peripheralsurface 2A of the inner ring 2. The narrow passage 19 allows air to passeasily, but it allows grease to hardly pass therethrough. That is tosay, the narrow passage 19 does not substantially allow grease to passtherethrough. Therefore, as indicated by arrows A in FIG. 1, greasemoving axially outwardly on the outer peripheral surface 2A of the innerring 2 is moved along the rake face 21 having a specified rake angle(about 45°) upon reaching the taper end portion 18. The rake angle ofthe rake face 21 may be smaller than 45°. The grease is, so to speak,scooped up by the rake face 21. Then, the grease moving along the rakeface 21 is guided along the cover portion 15 to the outer ring 1.

Therefore, according to the first embodiment, the possible leak ofgrease is substantially completely prevented.

Furthermore, according to the first embodiment, the axial extension 16includes the part 11A of the core metal 11 where the foremost end 11A-1is in the vicinity of the taper end portion 18. Further, the foremostend 11A-1 of the part 11A is located axially inwardly with respect tothe axial outermost end 2A-1 of the outer peripheral surface 2A of theinner ring 2. Therefore, the axial extension 16 is prevented from beingbent radially outwardly by a centrifugal force generated when the outerring 1 is rotated. Therefore, even when a centrifugal force is generatedon the axial extension 16 due to the rotation of the outer ring 1, thepossible leak of grease is always prevented substantially completely.Furthermore, by virtue of the existence of the foremost end 11A-1, aclearance between the axial extension 16 and the outer peripheralsurface 2A of the inner ring 2 is set with high accuracy.

Furthermore, the part 11A of the core metal 11 exists continuously in anannular form around the entire outer peripheral surface of the innerring 2. Therefore, the axial extension 16 is prevented from being bentradially outwardly by the centrifugal force throughout the entireperiphery. Therefore, even when a centrifugal force is generated on theaxial extension 16 due to the rotation of the outer ring 1, the possibleleak of grease is always prevented substantially completely.

In the first embodiment, the axial foremost end of the taper end portion18 has an acutely sharpened configuration. However, as shown in FIG. 1B,it is acceptable to provide a recess portion 25 that is recessedradially outwardly from the opposite surface 20 that forms the narrowpassage 19 and recessed axially outwardly from the foremost end of therake face 21 at the axial foremost end of the taper end portion 18. Withthis arrangement, the grease that has axially moved along the outerperipheral surface 2A of the inner ring 2 and reached the taper endportion 18 is firstly caught in the recess portion 25 at the axiallyinnermost end. Then, a mass F of the grease is retained in the recessportion 25. Therefore, an oil component of the grease is intercepted inthe mass F of the grease, so that the oil component of the grease isprevented from entering the narrow passage 19.

Furthermore, as shown in FIG. 1C, it is acceptable to provide a smallprojection 26 that is put in contact with the outer peripheral surface2A of the inner ring 2 on the opposite surface 20 of the taper endportion 18. The small projection 26 can slightly bend to thereby allowair to pass therearound. With this arrangement, the small projection 26intercepts a very small amount of the oil component of the grease, andtherefore the very small amount of the oil component of the grease isprevented from leaking through the narrow passage 19.

Second Embodiment

Next, FIG. 2 shows a second embodiment. The second embodiment is abearing sealing device arranged between an outer ring 31 and an innerring 32 of a bearing in which the outer ring 31 rotates, and seals aspace between the outer ring 31 and the inner ring 32. The bearing has aplurality of balls 33 arranged in an annular form between the outer ring31 and the inner ring 32. To the plurality of balls 3 is fitted acrown-shaped plastic retainer 35.

The second embodiment has a sectionally bracket-shaped core metal 41 andan elastic portion 42 that is made of an elastic material and fixedtightly to the core metal 41. The second embodiment includes a fixedportion 43 fit in and secured to a recess 34 at an axial end portionformed on an inner peripheral surface 31A of the outer ring 31, and acover portion 45 that extends radially inwardly from the fixed portion43 and covers a space between the outer ring 31 and the inner ring 32.The second embodiment further includes an axial extension 46 thatextends axially inwardly from the cover portion 45.

The axial extension 46 has a taper end portion 48. The taper end portion48 includes an opposite surface 50 that is opposed to the outerperipheral surface 32A of the inner ring 32 and forms a narrow passage49 between the opposite surface 50 and an outer peripheral surface 32Aof the inner ring 32, and a rake face 51 that forms a specified rakeangle (approximately 45°) with the opposite surface 50.

The axial extension 46 has two recess portions 52 and 53 located axiallyoutwardly with respect to the taper end portion 48. The recess portions52 and 53 are recessed radially outwardly by a specified dimension withrespect to the opposite surface 50 of the taper end portion 48. Theaxial extension 46 has an annular projection 55 that extendscircumferentially between the recess portions 52 and 53, and an annularprojection 56 that adjoins axially outwardly to the recess portion 53.The annular projections 55 and 56 have opposite surfaces 55A and 56Aopposite to the outer peripheral surface 32A of the inner ring 32. Theopposite surfaces 55A and 56A are arranged in approximately the sameradial positions as that of the opposite surface 50 of the taper endportion 48. Therefore, the opposite surfaces 55A and 56A form narrowpassages 57 and 58 between them and the outer peripheral surface 32A ofthe inner ring 32.

The core metal 41 has a part 41A that extends axially inwardly from thecover portion 45. The part 41A extends axially along the outerperipheral surface 32A of the inner ring 32 oppositely to the outerperipheral surface 32A, and its foremost end 41A-1 is positioned in thevicinity of the taper end portion 48. There are provided two recessportions 52 and 53 located axially outwardly with respect to the taperend portion 48. However, there may be provided three or more such recessportions.

According to the bearing sealing device having the above construction,the opposite surface 50 of the taper end portion 48 forms the narrowpassage 49 between the opposite surface 50 and the outer peripheralsurface 32A of the inner ring 32. The narrow passage 49 allows air topass easily, but it allows grease to hardly pass therethrough.Therefore, as indicated by an arrow A in FIG. 2, the grease movingaxially outwardly on the outer peripheral surface 32A of the inner ring32 is moved along the rake face 51 having a specified rake angle (about45°) upon reaching the taper end portion 48. The grease is, so to speak,scooped by the rake face 51. Then the grease moving along the rake face51 is guided along the cover portion 45 to the outer ring 31.

Furthermore, the grease that has accidentally passed around the taperend portion 48 is intercepted in the recess portion 52, and the greasethat has passed through the narrow passage 57 is intercepted in thesubsequent recess portion 53. Therefore, according to the secondembodiment, the possible leak of grease is more surely prevented.

Furthermore, according to the second embodiment, the axial extension 46includes the part 41A of the core metal 41 that is arranged oppositelyto the outer peripheral surface 32A of the inner ring 32, where theforemost end 41A-1 of the part 41A extends to an axial position in thevicinity of the taper end portion 48. Therefore, the part 41A canprevent the axial extension 46 from being bent radially outwardly by acentrifugal force generated when the outer ring 31 is rotated.Therefore, even when a centrifugal force is generated on the axialextension 46 due to the rotation of the outer ring 31, the possible leakof grease is always prevented substantially completely, Furthermore, byvirtue of the existence of the part 41A, a clearance between the axialextension 46 and the outer peripheral surface 32A of the inner ring 32is set with high accuracy.

Furthermore, the part 41A of the core metal 41 exists continuously in anannular form around the entire outer peripheral surface of the innerring 32. Therefore, the axial extension 46 is prevented from being bentradially outwardly throughout the entire periphery by the centrifugalforce. Therefore, even when a centrifugal force is generated due to therotation of the outer ring 31, the possible leak of grease is alwaysprevented substantially completely.

Third Embodiment

Next, FIG. 3 shows a third embodiment. The third embodiment differs fromthe first embodiment in the construction of a retainer 61 of thebearing. Therefore, the third embodiment will be described intensivelyon the retainer 61. It should be noted that the same elements as in thefirst embodiment are shown by the same reference numerals as in thefirst embodiment.

The retainer 61 has a projection 63 that projects radially inwardly froman inner radial portion 62. The projection 63 has an opposite surface63A arranged oppositely to the outer peripheral surface 2A of the innerring 2 axially inwardly with respect to the taper end portion 18, andthe opposite surface 63A forms a narrow passage 65 between the oppositesurface 63A and the outer peripheral surface 2A of the inner ring 2. Thenarrow passage 65 allows air to pass easily, but it allows grease tohardly pass therethrough. Therefore, according to the third embodiment,as indicated by arrows C in FIG. 3, the grease moving axially outwardlyis intercepted by the projection 63 before the taper end portion 18.Therefore, according to the third embodiment, the possible leak ofgrease is more surely prevented.

The retainer of the bearing is implemented by a crown-shaped retainermade of resin in the first through third embodiments, however, it may bea wave-shaped retainer made of iron. Furthermore, the sealing device isprovided axially on one side of the bearing in the first through thirdembodiments, however, it may be provided on both sides of the bearing.

Fourth Embodiment

Next, FIG. 4 shows a fourth embodiment. The fourth embodiment differsfrom the first embodiment only in the configuration of a retainer 5W.Therefore, the fourth embodiment will be described preponderantly on thepoint different from the first embodiment. It should be noted that thesame elements as in the first embodiment are shown by the same referencenumerals as in the first embodiment.

The retainer 5W supports the balls 3 arranged between the outer ring 1and the inner ring 2 axially inwardly with respect to the axialextension 16. The retainer 5W has a slant surface 5W-a arrangedoppositely and approximately in parallel to the rake face 21 of thetaper end portion 18. A distance L1 between the slant surface 5W-a andthe rake face 21 is set not smaller than a distance L2 (L1≧L2) betweenthe retainer 5W and the outer peripheral surface 2A of the inner ring 2.

It was found through an experiment that, when the balls 3 are rotatingwhile rolling between the outer ring 1 and the inner ring 2, thelubricating oil circulates in a route of (balls 3)→(a space between theouter peripheral surface 2A of the inner ring 2 and the retainer 5W)→(aspace between the rake face 21 of the taper end portion 18 of the axialextension 16 and the retainer 5W)→(a space between the cover portion 15and the retainer 5W)→(a space between the retainer 5Wand the outer ring1)→(balls 3) as indicated by void arrows in FIG. 4.

Therefore, the dimensional setting of L1≧L2 means that the lubricatingoil path through the space between the rake face 21 of the taper endportion 18 of the axial extension 16 and the retainer 5W is made widerthan the lubricating oil path through the space between the outerperipheral surface 2A of the inner ring 2 and the retainer 5W. With thisarrangement, the lubricating oil from the space between the outerperipheral surface 2A of the inner ring 2 and the retainer 5W is guidedto the space between the rake face 21 of the taper end portion 18 of theaxial extension 16 and the retainer 5W, and the lubricating oil ishardly introduced into the narrow passage 19 between the inner ring 2and the taper end portion 18. Therefore, the fourth embodiment has theeffect of preventing the lubricating oil from intruding into the spacebetween the inner ring 2 and the taper end portion 18. Therefore, incooperation with the sealing effect produced by the taper end portion18, the possible leak of the lubricating oil is more surely prevented.

Fifth Embodiment

Next, FIG. 5 shows a fifth embodiment. The fifth embodiment is arrangedbetween an outer ring 81 and an inner ring 82 of a bearing in which theouter ring 81 rotates, and operates to seal a space between the outerring 81 and the inner ring 82. The fifth embodiment has a bearingsealing device that is securely fixed to the outer bearing 81 and isrotated together with the outer ring 81.

The bearing sealing device includes a fixed portion 83, a cover portion85 and a seal portion 86. The fixed portion 83 is fixed to the outerring 81. The cover portion 85 extends radially inwardly from the fixedportion 83 and covers the space between the outer ring 81 and the innerring 82. The seal portion 86 extends radially inwardly and axiallyinwardly from the cover portion 85 toward an outer peripheral surface82A of the inner ring 82. The seal portion 86 has an opposite surface86A arranged oppositely to the outer peripheral surface 82A of the innerring 82. The opposite surface 86A forms a narrow passage 87 that allowsair to easily pass and allows oil to hardly pass therethrough betweenthe opposite surface 86A and the outer peripheral surface 82A of theinner ring 82. It is to be noted that a seal lip 91 has the samestructure as that of the radial extension 17 of the first embodiment andoperates to prevent the possible intrusion of dust.

Furthermore, the present fifth embodiment includes a retainer 90 thatsupports balls 88 arranged between the outer ring 81 and the inner ring82 axially inwardly with respect to the cover portion 85. In regard tothe retainer 90, a distance D1 between the retainer 90 and the sealportion 86 is set not smaller than a distance D2 between the retainer 90and the outer peripheral surface 82A of the inner ring 82. In practice,the distance D1 is set 1.8 times as great as the distance D2.

The dimensional setting of D1≧D2 means that the lubricating oil paththrough the space between the seal portion 86 and the retainer 90 ismade wider than the lubricating oil path through the space between theouter peripheral surface 82A of the inner ring 82 and the retainer 90.With this arrangement, the lubricating oil from the space between theouter peripheral surface 82A of the inner ring 82 and the retainer 90 isguided to the space between the seal portion 86 and the retainer 90, andthe lubricating oil is allowed to hardly intrude into the narrow passage87 between the inner ring 82 and the seal portion 86. Therefore, thefifth embodiment has the effect of preventing the lubricating oil fromintruding into the space between the inner ring 82 and the seal portion86. Therefore, in cooperation with the sealing effect produced by theseal portion 86, the possible leak of the lubricating oil is more surelyprevented.

Experimental Embodiment

A bearing having a structure similar to the bearing shown in FIG. 5 wassubjected to a grease leak experiment, and an analysis of the obtainedresults will be described below. In the present experiment, the bearinghas a shaft diameter of 38.2 mm. The present experiment was conducted bysetting a plurality of combinations of a distance A between a pressretainer 101 made of a soft steel and an inner ring 102, a distance Bbetween a seal portion 103 and the inner ring 102, and a distance Cbetween the retainer 101 and the seal portion 103 as shown in FIG. 6.Then, the grease leak amount of each combination was measured. Based onthe results of measurement, results of a single regression analysis ofthe distance A, distance B and distance C relative to the grease leakamount are shown in Table 1.

                  TABLE 1                                                         ______________________________________                                        <Correlation coefficient matrix>                                              (Single correlation)                                                                                              Leak                                      Variable      A         B              amount                                 ______________________________________                                        1A         1.0000  0.3235     0.9146                                                                              -0.6905                                   2B                 1.00005        0.2339                                                                             0.0256                                 3C                 0.23396        1.0000                                                                           -0.6848                                  4 Leak      -0.6905                                                                              0.0256     -0.6848                                                                                1.0000                                 amount                                                                        ______________________________________                                    

Table 1 is a correlation coefficient matrix. As apparent from Table 1,the grease leak amount has a strong correlation with the distance A andthe distance C, but it has a weak correlation with the distance B.Therefore, it is found that the distance A and the distance C areimportant in order to prevent the leak of the grease. Curvesrepresenting single regression expressions obtained from the results ofthe single regression analysis are shown in FIGS. 7 and 8. A regressioncurve representing the relation between the grease leak amount and thedistance A is shown in FIG. 7, while a regression curve representing therelation between the grease leak amount and the distance C is shown inFIG. 8.

Further, as the result of conducting a multiple correlation analysis ofthe distance A, the distance B and the distance C relative to the greaseleak amount, there was obtained a multiple correlation coefficientR=.[.0,744.]. .Iadd.0.744.Iaddend., where the correlation is significantat a level of dangerousness of not greater than 1%. That is, accordingto the results of the multiple correlation analysis, each of thedistance A, the distance B and the distance C has a strong correlationwith the grease leak amount. From the results of the multiplecorrelation analysis, the following Equation (1) was able to be derived.It is to be noted that the unit of the grease leak amount is gram, whilethe unit of the distances A, B and C is millimeter.

    (Grease leak amount)=(-1.976)A+3.14B+(-0.088)C             (1)

Then, by substituting B=0.2 (mm) and a leak amount=0.0 (g) into Equation(1) to simplify the equation, the following Equation (2) is derived.

    1.976A+0.088C=1.745                                        (2)

Meanwhile, it is found that the leak of the grease is prevented when(distance C).[.→.]. .Iadd.≧.Iaddend.(distance A) according to ahydromechanical way of thinking. Therefore, by substituting A=C intoEquation (2), C=0.85 is calculated.

Accordingly, there is derived the conclusion that the leak of the greasecan be prevented by satisfying the conditions of C≧0.85 mm and A.[.≧.]..Iadd.≦.Iaddend.C when the shaft diameter of the bearing is 38.2 mm.

The sealing device is provided on one side of the bearing in the fourthand fifth embodiments, however, it may be provided in spaces on bothsides in the axial direction.

The above embodiments employ balls as rolling members. But, rollers mayalso be used as rolling members.

The invention being thus described, it will be obvious that the same maybe varied in many ways. Such variations are not to be regarded as adeparture from the spirit and scope of the invention, and all suchmodifications as would be obvious to one skilled in the art are intendedto be included within the scope of the following claims.

What is claimed is:
 1. A .Iadd.bearing sealing mechanism for a bearing including an outer ring and an inner ring in which the outer ring rotates, and rolling members arranged between the outer ring and the inner ring, said bearing sealing mechanism comprising:a .Iaddend.bearing sealing device which is provided between .[.an.]. .Iadd.the .Iaddend.outer ring and .[.an.]. inner ring .[.of a bearing in which the outer ring rotates.]., seals a space between the outer ring and the inner ring, and is securely fixed to the outer ring so as to rotate together with the outer ring, .Iadd.said bearing sealing device .Iaddend.comprising: a fixed portion fixed to the outer ring; a cover portion which extends in a radially inward direction of the outer ring from the fixed portion and covers the space between the outer ring and the inner ring; and an axial extension which is made of an elastic material and extends in an axially inward direction of the outer ring from the cover portion, wherein the axial extension includes a taper end portion having an opposite surface which is opposed to an outer peripheral surface of the inner ring and forms between the opposite surface and the outer peripheral surface of the inner ring a narrow passage having a specified narrowness such that air is allowed to pass comparatively easily and oil is allowed to pass comparatively hardly, and a rake face forming a specified rake angle with the opposite surface; and the fixed portion, the cover portion and the axial extension respectively include part of a core metal, said core metal extending axially inwardly from the cover portion up to a position on a radially outer side of the outer peripheral surface of the inner ring, where a foremost end of the core metal is positioned in the vicinity of the taper end portion.Iadd..[.;.]. .Iaddend.and a retainer which holds the rolling members arranged between the outer ring and the inner ring axially inwardly with respect to the axial extension wherein said retainer has a configuration such that a distance L1 between the retainer and the rake face of the taper end portion of the axial extension is larger than a distance L2 (L1>L2) between the retainer and the outer peripheral surface of the inner ring.
 2. A bearing sealing .[.device.]. .Iadd.mechanism .Iaddend.as claimed in claim 1, wherein the taper end portion comprises at its axial innermost end a recess portion which is recessed radially outwardly from the opposite surface that forms the narrow passage and recessed axially outwardly from a foremost end of the rake face.
 3. A bearing sealing .[.device.]. .Iadd.mechanism .Iaddend.as claimed in claim 1, wherein the axial extension comprises:a recess portion which is located axially outwardly with respect to the taper end portion and recessed radially outwardly with respect to the opposite surface of the taper end portion.
 4. A bearing sealing .[.device.]. .Iadd.mechanism .Iaddend.as claimed in claim 1, wherein the part of the core metal in the axial extension has an annular configuration existing continuously around an entire outer periphery of the inner ring. .[.
 5. A bearing sealing mechanism comprising:a bearing sealing device as claimed in claim 1; and a crown-shaped retainer which is made of resin and holds rolling members arranged between the outer ring and the inner ring, whereinsaid retainer has a projection including an opposite surface that is provided oppositely to the outer peripheral surface of the inner ring axially inwardly with respect to the taper end portion, and forms between the opposite surface and the outer peripheral surface of the inner ring a narrow passage having a specified narrowness such that air is allowed to pass comparatively easily and oil is allowed to pass comparatively hardly..]..[.6. A bearing sealing mechanism comprising: a bearing sealing device as claimed in claim 1; and a retainer which holds rolling members arranged between the outer ring and the inner ring axially inwardly with respect to the axial extension, whereinsaid retainer has a configuration such that a distance L1 between the retainer and the rake face of the taper end portion of the axial extension is set not smaller than a distance L2 (L1≧L2) between the retainer and the outer peripheral surface of the inner ring..]..[.7. A bearing sealing mechanism comprising: a bearing sealing device which is provided between an outer ring and an inner ring of a bearing in which the outer ring rotates, seals a space between the outer ring and the inner ring, and is securely fixed to the outer ring so as to rotate together with the outer ring; and a retainer which holds rolling members arranged between the outer ring and the inner ring axially inwardly with respect to the bearing sealing device, whereinsaid bearing sealing device has a fixed portion fixed to the outer ring a cover portion which extends radially inwardly from the fixed portion and covers a space between the outer ring and the inner ring, and a seal portion which extends radially inwardly and axially inwardly from the cover portion toward an outer peripheral surface of the inner ring, said seal portion having an opposite surface which is opposed to the outer peripheral surface of the inner ring, and forms between the opposite surface and the outer peripheral surface of the inner ring a narrow passage having a specified narrowness such that air is allowed to pass comparatively easily and oil is allowed to pass comparatively hardly, and wherein said retainer has a configuration such that a distance D1 between the retainer and the seal portion is set not smaller than a distance D2 (D1≧D2) between the retainer and the outer peripheral surface of the inner ring..]. 